Perhaps you should try some spelling variations:
van nang » van quang, van ban, van dung
cau thuc » cau truc, cuu thuc, can thuc
thuc ban » thuoc ban, thuc dan, thu ban
ban hanh » ban hang
so sach » so sanh, bo sach, co sach
hieu ve » hieu va, hieu van
ve cau » ke cau, va cau, ve cac
de cua » le cua, dieu cua
te cua » tue cua, le cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ((van nang) OR (van dong)) xa hoi. hieu ve cau thuc ban hanh ((de cua) or (te cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((van nang) OR (van dong)) xa hoi. hieu ve cau thuc ban hanh ((de cua) OR (te cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((van nang) OR (van dong)) xa hoi. hieu ve cau thuc ban hanh ((de cua) or (te cua)) tre".
• Adding a wildcard symbol may retrieve word variants: so sach ((van nang) OR (van dong)) xa hoi. hieu ve cau thuc ban hanh ((de cua) or (te cua)) tre*.